Don't get stuck: Match the glue to the project

Q. I need to glue pieces of wood together and have never done it. It’s in my best interest to get this right the first time, so can you share some tips with me? I have both interior projects to do, and some where the wood will be outdoors. I realize there are different glues to use, but am more concerned with technique. Help me please.

A. You came to the right place. I’ve glued many things together over the years, using all sorts of products. What I’ve discovered is that most of them deliver fantastic results if you just use them according to the directions and add some common sense along the way.

Photo/Tim CarterTo glue wood to wood effectively, both wood surfaces need to be clean and at room temperature. Clamping is a must.

You do need to match the glue to the project, as some glues are not formulated to withstand exposure to water once they’ve dried and cured. Other glue products are waterproof. You usually can find out by reading the label of the product. If you don’t see any wording on a glue label stating that it’s waterproof, assume that it’s not.

If you want great results when gluing two pieces of wood — or anything for that matter — it helps to think on a micro scale. Imagine what’s happening where the glue is interacting with the wood, glass, plastic or metal.

Without getting into complicated chemistry or physics, realize the glue is trying to act like a burr or briar that might attach to your clothes as you walk through the woods. Dried glue has a structure that has minature hooks, barbs, etc. that try to latch on to the surface upon which it’s spread.

NO DUST

This means the surface should be free of all dust, dirt and oil, and it helps if the surface is somewhat rough. The roughness creates more surface area for the glue to grab onto and it creates more places for the tiny hooks and barbs to attach themselves.

Temperature is also a consideration. Most glues you’ll find at stores have a water base and should be used at temperatures that range from 50 F to 90 F. Again, reading the label will tell you if there is a preferred temperature range.

The common yellow glues that are water-based work as the water evaporates or soaks into the wood. As the water leaves, what’s left behind is the actual glue that does the work. Think of the water as a delivery vehicle.

Some other glues have a totally different chemistry and require the surfact to be wet or that there be significant humidity in the air for the glue to react and bond. Once again, read the label and do what the manufacturer says with respect to wetting the surfaces slightly.

Perhaps the most common mistake people make when using wood glues is failing to clamp or apply pressure to the objects being glued. There are numerous ways to achieve this goal, including hand clamps, pipe clamps, weight, screws and nails. The object is to do whatever is necessary to squeeze the pieces of wood together for as long as the instructions say to apply the pressure. Clamping time can be as short as 30 minutes or an hour. PUT THE CLAMPS ON

I can tell you from experience that the longer you clamp things, the better the job will turn out. I don’t mean clamp things for days; however, extending the clamping time by 50 to 100 percent of the time mentioned on the label is not a bad idea.

Remember: The clamping time was probably set assuming the objects being glued are just around 70 F in temperature. If it’s colder than that where you are doing the work, you need to extend the clamping and curing time to get maximum holding power.

It’s important to think about the specific qualities of what’s being glued. For example, the end grain of wood pieces will readily soak up glue. If you’re gluing end grain, spread some glue onto the end of the piece and move it around with your finger or a stick. Wait about two minutes to see if the glue soaks in.

If it does, add some additional glue before you clamp the pieces together to ensure there will be enough left at the joint to do the job. I’ve seen my own work fail because all the glue soaked into the end grain, not leaving enough behind for a proper bond.

Watch a wood glue video and read past columns about different wood glues at www.AsktheBulider.com. Just type “wood glue video” into the AsktheBuilder.com search engine.